ABSTRACT
We consider the sequence of earthquakes on the Parkfield segment of the San Andreas fault to be representative “characteristic” earthquakes. We consider the recurrence interval statistics of these earthquakes and the frequency-magnitude statistics of smaller earthquakes prior to the 2004 Parkfield earthquake.We give results for a “stiff” slider-block model and show strong similarities between the model and the Parkfield results. In both cases a power-law distribution of smaller events were observed. In both cases theWeibull fit to the distribution of interval timeswas quite goodwith similar values of the power-lawexponent.Wehave also drawn an analogy between an earthquake rupture and a first-order phase change (nucleation). We consider this analogy both with and without damage. With damage the rupture is equivalent to an equilibriumphase change, without damage the rupture is equivalent to a spinodal phase change. We argue that the absence of a systematic precursory acceleration of seismicity prior to earthquakes is evidence that precursory damage does nor occur. Thus fault rupture can be associated with a spinodal phase change.
